Telephone system



M. LANGER.

TELEPHONE SYSTEM.

APPLIEATION FILED NOV- l3| 1919.

' 404,39 Patented Jan. 24,1922.

5 SHEETS-SHEET I.

M. LANGER.

TELEPHONE SYSTEM.

APPLICATION man NOV- 13, m9.

1 ,404,396, Patented Jan. 24, 1922.

M'. LANGER. TELEPHONE SYSTEM.

I APPLICATION FILED NOV. 13, I919. 1,404,396, Patented Jan. 24, 1922.

5 SHEETS-SHEET 3. P)

M. LANGER.

TELEPHONE SYSTEM.

APPLICATION FILED uov.13. I919.

1,404,396, Patented Jan. 24, 1922.

5 SHEETS-SHEET 4.

M. LANGER. TELEPHONE SYSTEM. APPLICATION FILED Nov.Ia.191'9.

Patented Jan. 24, 1922. v 5 SHEETS-SHEET 5.

MAX LANGER, OF CHARLOTTENEURG, NEAR BERLIN, GERMANY, ASSIGNOR TO SIEMENS & HALSKE .A.C-.., Oil SIEMENSTADT,

CORPORATION 035 GERI'JIAITY.

NEAR BERLIN, GERMANY, A

TELE1 HON E SYSTEM.

1,494,39f1 Specification of Letters Patent.

Original application filed June 23, 1914, Serial Patent No. 1,322,247, dated llovernber 18, 1919. Serial No. 337,745.

To all whom it may concern:

Be 1t known that 1, MA}: Lancer, a Gerf J-- v man citizen, and resident oi bliariottenbuig, near Berlin, Germany, have invented certain new and useful improvements in Telephone Systems, of which the following is a specification.

This invention relates to telephone systems,.the present application being a division of my application Serial No. 8 33,2313, filed June 28, 1914; renewed as Serial llo. 289,13i, April 10th, 1919, now Patent No. 1,322,247, Nov. 18th, 1919.

The object of this invention is to enable the metering of calls in telephone systems in which connections are established over selectors or switches and testing takes place over the talking wires. For this purpose measured service devices and circuits are included in the telephone system with a view to enabling the metering of calls, wl en the receivers are replaced to the hooks at the stations.

Another object of the invention is to pro vide means whereby the calls may be metered as soon as the called subscriber takes oil his receiver from the hook.

In the drawings two modifications are diagrammatically shown by way of exampl Figs. l-3 represent telephone which the calls are metered as soon as calling subscriber as well as the called sunscriber replace their receivers to the hooks, respectively.

Figs. 2, 5 represent a telephone system in which the metering takes place when the called subscriber takes oil his receiver from the hook.

In the telephone system shown in the drawings all relays and contacts operated thereby are represented in their normal positions. A

The operation of the telephone system show i in is as follows:

When the receiver is removed from the switch hook at the station N the following circuit is closed: ground, battery, left hand winding o1 relay B back contact 6 line conductor a, station N line conductor Z), back contact 25 right hand winding ct relay R ground. lVhen the wipers or" the line switch VlV are advanced until the private No. 846,013. Renewed April 10, 1919, Serial No. 289,134.

Patented Jan. 24, 1922.

Divided and this application filed November 13,

wiper co engages an idle trunk line, whereupon a circuit is completed from ground through battery, working contact 73 in parallel through the relays T and Z, wiper co, line 0, resistance 10 through resistance Q02, back contact m to ground, and, at the same trme, 111 parallel through winding 1 of relay (l, primary off-normal contact 0 to ground. In this circuit the meter relay Z is not ener gized whereas the relays T and C are energized and, therefore, the working contacts 6 6 L, are closed. Consequently the following circuit is completed: ground, battery, relay A left hand winding of the differentially wound relay X, trunk line a, working contact 25 station N trunk line Z), work ing contact 5,, right hand winding of relay X, relay 3,, ground. Since the back contact is opened the rotary magnet Do of the line switch Vll becomes (lo-energized. The voltage drop causel by the closing ot the working contact t does not sultice to energize the relay Z. As soon as the calling subscriber operates his callingdial in the usual manner the relay B is grounded at the station N lVhen the relay B is Inomentarily de-energized the differentially woiind relay X is energized. As the calling dial returns to its normal position the relay 3, is again energized by the following circuit: ground, battery, working contact Q31, relay 3,, ground. The relay l 1 practically remains energized until the talking connection is released. he relay X also closes its working contact m th reby preparing a circuit for the vertical magnet H from ground battcrv. ignetll secondry oil-normal contact 107a,, back contact a of the relay A working contact an to ground. lVhen the dial is returning to its normal position the current impulses sent over the trunk line a; are transmitted to the vertical magnet H of the first selector LGVV by the operation of the working contact a of the relay A,. As soon as the dial has returned to its normal position the ground at the station N is removed and the armature of the relay X released, whereas the relay 13, remains energized. During the current impulses the oil-normal contact 75 in the circuit of the winding 1 of the relay C is opened at the first step of the shaft of the first selector LGW. The winding 1 of the relay C remains grounded, however, in a circuit extending over its own working contact 0 working contact 00 of the relay X, and the back contact m of the relay M At the first step of the shaft of the first selector LGW the primary ofi-normal contact is, is closed. Since, however, the back contact Z2 has been opened by the relay 13,, the relay S remains de-energized. After the last impulse for the first digit being transmitted the ground at the station N is removed. T here tore, the relay X de-energizes and opens the circuit of the relay C at the contact ((2,. At the same time the working contact :0 is opened, the vertical magnet H having been tie-energized by the opening of contact (4,.

The rotary magnet D will now become energized in a circuit from ground, battery, interrupterllb relay D back contact 0 working contact 6 to ground, and rotates the wipers of the first selector LGVi until the relay C is energized again. This occurs at the moment the wipers 7' j, engage a trunk line VL leading to an idle second selector ILGW (see Fig. 2) thereby establishing the following circuit: ground, battery, relay A oit' the second selector IIGVV,

- primary oitnormal contact back contact 39 wiper j working contact 5 second winding :2 of the relay C, back contact 0 wiper back contact 32 primar off-normal contact 70 back contact (6,, ground. When the relay C thus operating as a private magnet is energized the circuit of the rotar magnet D is broken at the contact 0 r t the same time the contacts 0,, 0,, 0 are closed thereby extending the connection to the selector TTGVV and establishing a holding circuit for the relay C from ground, battery, working contact 6 in parallel through relay Z and relay T, wiper on, resistance 20,, winding 1 0i relay C, working contact 0 secondary oilnormal contact @070 back contact m to ground. This holding circuit remains established until the connection is released. As soon as the shaft of the first selector IGW' is rotated the secondary oil-normal contact ".070 is opened thus preventing a reenergization of the vertical magnet H The relay A, upon energizing closes the working contacts a a a, and opens the back contacts a a a By the closing of the working contact a, a. guarding potential is established extending from ground, battery, relay 13,, working contact a primary off-normal contact 70 back contact 7),, trunk line Z) (see Fig. 2), wiper (see Fig. 1'), working contact 0 working contact (4,, back contact 22 resistance 10,, back contact a, to ground. The relay A remains energized in the following circuit: ground, battery, relay A primary elf-normal contact 70 back contact 39,, wiper y' working conthe 7 tacts 0,, (4,, back contact-o resistance 10 back contact 8,, ground.

When now the calling subscriber oper ates his dial for the second digit the relay X is energized again 'and,therefore, both trunk lines a and b in the first selector lGlV are grounded at During the second digit o f current impulses the relay A, is ale-energized, accordingly, thereby the working contacts ca and a, are broken and the ground is removed from the trunk lines a and b at the contact The relay l3 remains, however, energized in circuit over the resistance w and the contact :0 Dun ing the current impulses the relay A, becomes (lo-energized, accordingly. Therefore, the contact a, is opened and the contact a is closed. The opening and closing of these contacts does not eiiect, however,

a de-energization of the relay 13, since its circuit is closed by the working contact 32,. By the closing of the contact a, the circuit for the vertical magnet/h of the second selector TIGW is completed: ground, battery, vertical magnet H working contact b backcontact a ground. as the vertical magnet H isv energized the wipers y',, y, of the second selector ILGV? are operated. At the first step o f the shaft oi? thev second selector 11.6.73 the primary off-normal contact 70 is opened. The relay A however, remains energized in a circuit over the resistance Q04 as well as over the working contact After the last impulse for the second digit being transmitted the ground at the station U is removed. Therefore, the relay X becomes dc-energized so that the working contact 00 is opened, thus the ground is removed from the trunk lines a, Z), and the relay B die-energized. Since the working contact b is opened the vertical magnet H becomes de-energized. The contact 6 being closed a circuit is prepared for the rotary magnet D mains energized in a circuit extending from ground, battery, relay A, resistance 10,, back contact 29 wiper 9' working contacts 0,, (6,, resistances 10 w back contact to ground. Since the relay A, is energized and the relay l3 de-energized a circuit is established for the rotary magnet 1),: ground, battery, interrupter U rotary magnetl). working contact a back contacts 79 A, primary oft-normal contact 71,, ground. Thewipers j,, j, of the second selector TTGWV are rotated until they engage a trunk line leading to an idle third selector lILGlV. V

The circuit for the rotary magnet D remains established until the contact 29, is opened. The contact 6 in "the same circuit remains closed since the relay-B does not attract its armature again before the winding 2 of the relay P is energized.

As soon The relay A, re-

The test circuit of the Second selector ILGW is as follows: ground, batter, relay A primary off-normal contact back contact 39 trunk line a, wiper j working contact (4,, back contact 7),, winding 2 of relay 1 wiper i back contact 22 primary off-normal contact 76 back contact (a to ground. The wipers of the second selector ELGc-VV are advanced until an idle third selector IILGVV is found. A third selector is idle if the back contact a of the relay A, is connected toground, and if the trunk line a is connected by the relay A, of the third Selector IILGVV to battery. As soon as an idle third selector IILGXV is found the following circuit is established: ground, battery in the third IILGV, relay A,, primary off-normal contact h back contact 2 trunk line a, wiper j working contact 05,, back contact b winding 2 of the relay P wiper 5' trunk line I), back contact 10 primary olfnormal contact 7c back contact a ground. In this circuit the relay P is energized and the operating circuit for the rotary magnet D opened at the contact 9 Therefore, the second selector ILGlV extends the connection to the third selector IILGVW. The relay P, in the second selector IIGN being energized the contacts and 7), are opened and the contacts p 7),, 3),, p, re closed. The connection is thus extended by the working contacts 2), and p, to the third selector IILGW.

The operation of the third selector IIIGTV in extending the connection to the connector LlV is substantially the same as of the second selector ILGW.

As soon as an idle connector has been found the test relay P of the third selector IILGTV and the relay A, of the connector LY? are energized. Therefore, the back contact a is opened and the working contact a, closed, so that the relay B i is now included in a circuit over the working contact a,. Thus the relays A, and B are energized. If now the subscriber operates his dial for the fourth digit the relay X of the first selector LGlV is energized thereby closing the contact :0 During the interruption of the loop at the station N the relay B remains energized during the emission of impulses in the following circuit: ground, battery, relay 13,, back contact 3 working contact 6 back contact 19,, trunk line b, wiper j working contacts 0,, a 4a,, ground. The relay B being energized the contact I), becomes closed and the vertical magnet I-I energized in the following circuit: ground, battery, vertical magnet H back contact 14,. working contact 12,, back contact a, ground, so that the shaft of the connector is operated. At the end of the impulses sent out by means of the dial at the station N, the relay X becomes tie-energized and, therefore, the

selector contact a, is opened. The trunk line a is now included in a circuit extending from ground, in the first selector lGlV, back contact 5,, resistances 20,, 10 working contacts a 0,, wiper 7' working contacts 77,, p winding 1 of relay 1 relay in the 0nd selector ILGlV, battery, ground. Another circuit is established from contact 12,, trunk line a, wiper 7' working contact 37 relays P and A,, battery, ground, and a third circuit extending from working con tact 12 trunk line a, wiper back contact {0 resistance co back contact g relay A, battery to ground. In the second selector ILGlV the relay A, as well as the relay P, remain energized although the winding 2 of the relay P, has become (lo-energized. Therefore, the relays A A A, and A are energized.

Since no current is flowing in the trunk line b in the connector LlV the relay B, releases its armature. Therefore, the back contact 6 is closed and the relay U energized in the following circuit: ground, battery, re lay U, back contact a working contact (6 primary off-normal contact 7;,, ground. The primary off-normal contact 70 has been closed at the beginning of the operation of the shaft of the connector l The relay U closes the working contact a, and remains energized independently of the condition of the relay B, until the primary off-normal contact 70 is opened by the operation of the connector LlV when returning to normal position. By the operation of the relay U the back contact a, is opened and the working contact 24 closed; Since the relay X becomesde-energized the working contact 02, is opened so that the slow acting relay V becomes de-energized. If, therefore, the contact o, of the relay V is closed sometime afterwards the following circuit is established again in the first selector: ground, back contact s resistance '20,, back contact 4),, working contacts cf, 0,, wiper 7' working contact 0 wiper 7;, working contact 22 wiper y back contact 2),, working contact 6%, back contact y relay 3,, battery, ground.

when the subscriber rotates nis dial for the last digit of current impulses the relay X is energized again. The contact (a, in the first selector LGW is closed and the contact o, opened. Thus the circuit over the trunk line 7) remains established since this line remains grounded by the contact u The circuit over the trunk line a is intermittently interrupted in accordance with the interruptions caused by the dial switch. The relays A, and A, in the first selector LGlV and in the connector, respectively, become ce-energized in accordance with the interruptions referred to. The rotary magnet D, in the connector LlV is energized by the following circuit: ground, battery, relay 1),, working contacts u 6,,

. contact 22 back contact a ground. Together with the rotary magnet D the slow acting relay V is energized by the circuit: ground, battery, relay V working contacts M3, 6 back contact a ground.

The last series of current impulses having been sent out the contact w, in the first selector is opened, so that the trunk line 7) is currentless. Therefore, the relay B in the connector becomes ale-energized and releases its armature. The relay V in the connector, however, still remains energized for some time since it is slow-acting. A testing current for the connector is then established from ground over back contacts m 9,, working contact '23,, back contact b relay P wiper (a0 01 the connector LW, contact 9 of the line switch VV of the called subscriber N relay T primary oilnormal contact k battery, ground. The test relay P of the connector is energized thereby. Sometime afterwards the contact c of the slow-acting relay V in the first selector'TJGlV w ill become closed. The relay B in the connector is thereby energized again. The test relay P of the connector Ll'V remains energized since it has been included in a. holding circuit by its working By closing this contact 10,, a portion of the winding of the relay P is short-circuited so that the called line is rendered busy. By the energization of the test relay P, the working contact 11 is closed and the back contacts 79 223 opened. The relay A, remains energized over the contact resistance 10, contact 79 trunk line a, wiper 3' working contact p wiper 7' working contact 19 wiper y' working contacts 0 a resistances 20,, co back contact 8 to ground. At this moment no circuit is established over the trunk line b. It then the relay V in the first selector lGlV becomes de-energized and the contact o closed a current will flow over the trunk line Z) in the following circuit: ground, contact 8 resistance ic back contact o resistance "m working contact 0 wiper j working contact p wipr 71,, working contact p wiper resistance w working contact a back contact 3 relay B battery, ground. It is immaterial whether the circuit through the relay 13 includes the resistance w or not since the relays A, and 13,, do not aifect the line-connection it they are simultaneously energized or deenergized. Thus the bridge in the connector comprises the following circuits: one circuit from ground, battery, relay A contact g resistance w working contact 2), to trunk line a. and another circuit from ground, battery, relay 13,, back contact 3 working contact a and in parallel over back contact 6 resistance 10 to the trunk line Z As soon as the tes relay circuit of the call relay L is closed as well as the contacts p andp in the trunk line a, 6. Since the relay'V is slow-acting it is still energized when a calling circuit is established for the called station N as follows: ground, battery, winding 2 of the call relay L, working contacts 10 back con tacts 1 rimary ofli-n0rmal contact ground. the first movement of the connector LVV.

he relay L opens its contacts Z Z and closes the contacts Z Z Therefore, a calling current is sent to the called station N, as soon as testing takes place. As soon as the relay V, has become de -energized additional periodic calling current impulses are sent by the excited winding 1 of the rela r L in the following circuit: ground, battery, interrupter U5 winding 1 of the relay L, working contact 29,, back contact 2 primary elf-normal contact 75,, ground. These periodic callingcurrent impulses are sent to the station N until the called subscriber takes oti his receiver from the hook. When the called subscriber takes oil his receiver -from the hook the following circuit is closed: ground, battery, winding 1 of the relay Y, back contact 7-,, working contact p station N working contact 72 back contact 1,, relay F, ground. The relays F and Y are energized in this circuit and the back contacts y, and g opened and the working con tacts and 3/6 closed, respectively. The relays A, and B now become tie-energized, and an inductively wound relay 0 having the middle of its winding grounded is connected. to the trunk lines a and Z). The ground connection at the relay 0 in the connector is now in parallel with the ground at the contact 3 in the first selector at the talking lines of the trunk.

If after conversation the called subscriber N should replace his receiver to the hook before the calling subscriber N, has replaced his receiver, the relay F becomes de-energized. The relay Y, however, remains energized in a circuit over its holding winding 2. Thus a relay G is energized in the following circuit: ground, battery, relay G; working contact back contact f ground. The relay Gr opens its contact {/1 so that the relay P becomes de-energized. Therefore, the contacts p p and are opened so that the called station N is released. Therefore, the subscriber of the station N may be called by or call another party although the connector LVV engages the trunk lines leading to said station N It now the calling subscriber N replaces his receiver to the hook the relays A, and B in the firstselector LGW are tie-energized. Assoon as the contact 6 has been closed the relay S is error gized in the following circuit: ground, battery, relay S, primary off-normal contact 7a,, back contact 5 ground.

This call is now metered at the end of the he contact ]c has been closed at conversation and then the talking connection between the two stations N, and N released.

In the first selector the back contact 8", is opened and the working contact 8, closed. Thus a meter relay Zr is now included in the circuit. Since the trunk line a. b is grounded only at the relay 0 in the connector LIV, this ground connection establishes a circuit for the meter bridge in the first selector ILGVV and for the relays A B in the second selector IIGW as well as for the relays A,, B in the third selector IIIGYV. The current in the relay 0 is thereby strengthened to such an extent that the relay 0 attracts its armature. At the same time the meter relay Zr in the first selector IGIV is energized. Therefore, the contact .27 is closed and the resistance 10, short-circuited thereby, so that the current in the test line 0 is increased and the meter Z energized in the following circuit: ground, battery, working contact 22,, meter Z, wiper or, working contacts e l-' 3 secondary off-normal contact 1070 back-contact m ground. In View of the short circuit around the relay 0 this relay C becomes de-energized. The contacts 0 0 are opened. At the same time the following circuit for the releasing magnet M of the first selector LGl V is closed: ground, battery, relay M working contact .9 back-contacts c Z2 ground. W hen the shaft of the selector has returned to normal position the circuit for the relay S is opened at the primary off-non mal contact 7a,. Therefore, the contact a, is opened and the releasing magnet M, deenergized. The line switch VIV returns to normal position if the releasing magnet M has become energized and the back contact m, opened.

By the energization of the relay O the connector LW is released. This releasing operation is caused by the releasing magnet M, being energized in the following circuit: ground, battery, relay BL, working contacts 3 0,, ground. As soon as the connector IJW returns to its normal position the contacts it 70 are opened. The relays U and Y as well as the releasing magnet M become Clo-energized. lVhen the relay Y is de-energized the circuit through the relay 0 is broken at the contacts 9 The trunk lines a and b are now again connected with the battery over the relays A, and 13,, no gromid connection xistin with said trunk lines either in the first selector IGW or in the connector LIV.

In the second selector IIGW the following releasing circuit is closed: ground, battery, releasing magnet M back contacts a 7J3, 6 primary off-normal contact 10 ground, and in the third selector IILGW: ground, battery, releasing magnetM back contacts a 12 6 primary off-normal contact 70,, ground. These releasing circuits remain estab'lished until the primary off-normal contacts 7c, and 7c, are opened when the shafts of said selectors arrive at their normal positions.

If the called subscriber M does not take off his receiver from the hook or if the desired subscribers line is busy no metering takes place. In this case the relay Y is not energized. Thus the relay 0 is not connected to the trunk lines. If, therefore, the calling subscriber N, replaces his receiver to the hook the relays A, and B in the first selector IGVV are de-energized, the relay S is energized and the ground connection broken the opening of the back contact s Since, however, the relays A and B in the connector LlV are not connected to ground over the relay 0 the meter relay Z1" is not energized. Therefore, in all selectors the trunk lines are still connected to battery and the selectors return to their normal positions. The relays A and B become tie-energized. In the connector LW the following releasing circuit is closed: ground, battery, releasing magnet M back contacts 2 L primary off-normal contact 70 ground. The primary off-normal contact 70, is opened soon the shaft of the connector arrives at its normal position.

Referring to Figures 2, i and 5 a telephone system is shown in which metering takes place when the called subscriber takes off his receiver from the hook. In this modification one low resistance coil of the relay Zr, is included in the ground connection of the contact w, and another coil of the relay Zr, in the ground connection of the contact 8,. A slow-acting relay Q is connected in parallel with the rotary magnet D In the circuit including the resistance 10,, by which the current in the line 0 is so increased that the meter Z is operated, a working contact 6 a secondary off-normal contact 0.07 a back contact of the meter relay Zr and the back contact (1 of the relay Q are provided. By means of a weight Cr? lifted by the shaft of the connector LW bridge connection is established over the contact springs The meter operation takes place as follows: If the called subscribed N takes of? his receiver from the hook a short circuit around the resistance 20, is established over contact 5 primary oil-normal contact wt contact er, contact The relay B, in the selector IGW is energized from the time the selector is busy until the moment when the calling subscriber replaces his receiver to the hook. During this time the contact 5 is also closed. When the rotary magnet of the selector is energized the contact g is opened and the secondary elf-normal contact wk, of the selector is closed afterwards. If the selector meets a disengaged line the relay C is energized again. The relay Q, however, remains energized for a moment and, therefore, the back contact q remains open.

metering takes place.

If the working contacts 0, and e, have become closed, as described in connection with the system shown in Figs. l3 the following circuit is closed (see Figures 4, 2, 5): ground, battery, relay A resistance 1a,, back contact 79 wiper 7' working contacts (a, 0,, back contact '0 resistance w winding 2 oi the relay Zr, back contact 8,, ground. In this circuit the meter relay Zr is energized. Thus the back contact er in the short circuit around the resistance 10 is opened before the back contact Q is closed again. A holding circuit is permanently closed over either the trunk line a or the trunk line I) of the next selector, as described in connection with Figs. l-3. This'holding circuit is connected to ground either by the contact a, or the contact (E4. The meter relay Zr thus permanently remains energized either with reference to its winding 1 or its winding 2. When the called subscriber N takes off his receiver from the hook, the relay Y in the connector LW is energized and the contact gy closed thereby. The weight GWV is released and when moving downwards temporarily closes the contacts 2 Both trunk lines are grounded by the contact 3 and the winding 2 of the relayZr in the first selector LGW is shortcircuited. The relay Zr in the first selector is de-energized'during the time the-weight GW in the connector operates the contacts z so as to be closed. In the short-circuit around the resistance w the contact 21' is closed and the meter Z energized thereby. When the weight GW in the connector has passed the contacts 2 the short circuit is removed and the relay Zrin the selector energized again, thereby diminishing the current in the line a.

If the called subscriber does not take olt his receiver from the hook jno metering takes place. Though the weight Gi l is lifted by the-shaft of the connector and the contacts 2, are closed by the weight no .op-'

eration of the meter {takes place when releasingthe connector since the established connection is released by the relay 3, in the first selector becoming de-energized. As soon as the relay B, has becomelde-energized the contact Z2 in the short-circuit around the resistance w, is opened. Thus it is irrelevant whether the, relay Zr is still closed for some time or opened. Since the meter cir cuit extends symmetrically over the two trunklines the test relay of an adjacent selector is connected with the'same potential so that it is not energized at the moment If it is intended to have metering take place only about six or seven seconds after the beginning of the conversation with a view to enabling the calling subscriber to ascertain the number or name of the called subscriber during this time, the weight GW may be provided with a retardation device ing which establishes the short circuit around the springs 2 after said predetermined time. It the calling subscriber has ascertained that the subscriber who answers is not the trunk lines, the combination with the trunk lines of test relays associated with the trunk lines and havingcoils adapted to be connected at the one end to the one talking wire of the trunk line and the other end to the other talking wire, and means associated with the trunk lines for taking reduced potential to said talking wires when the trunk line is busy; service meters associated with the telephone lines, means for mterconnecting said meters with the trunk lines when the telephone line is calling, means atthe called end of the connection for producing animpulse in the trunk lines when the conversation takes place, and means for transmitting said impulse to the metertor registering the conversation.

2. In an automatic telephone system comprising telephone'lines, trunk lines each havingtwo wires, and switches'andselectors for interconnecting said telephone lines with trunk lines, the combination with'thetrunk lines of test relaysassociated with the trunk lines and having coils adapted to be connected at the one end to the one talking wire of the trunk line, and the other end to the other talking wire, and means associated with the trunk lines for taking reduced potential to said talking wires when the trunk line is busy; service, meters associated with the telephone lines, means for interconnectsaid meters with the trunk lines when the telephone line is calling, means at the called end of the connection for producing an impulse in the trunk lines when the conversation takes place, means for transmit-- ting said impulse to the meter for registering the conversation, and-means for preventing the disconnection of the talking connectioln established during the flow of the impu se.

3. In an'automatic telephone system com. prising telephone lines, trunk lines each having two wires, and switches and selectors for interconnectin said telephone lines with trunk lines, thecom-bination with the trunk lines of test relays associated with the trunk hues and having coils adapted toibe connected at the one end to the one talking wire of the trunk line and the other end to the other talking wire, and means associated with the trunk lines for taking reduced potential to said talking wires when the trunk line is busy; service meters associated with the telephone lines, means for interconnecting said meters with the trunk lines when the telephone line is calling, means at the called end of the connection for producing an impulse in the trunk lines when the conversation takes place, means for transmitting said impulse to the meter for registering the conversation, means for preventing the discon nection of the talking connection established, and means to make busy the said connections during the flow of said impulse.

i. In an automatic telephone system comprising telephone lines, trunk lines each having two wires and switches and selectors for interconnecting said telephone lines with trunk lines the combination with the trunk lines of test relays associated with the trunk lines and having coils adapted to be connected at the one end to the one talking wire of thetrunk line and the other end to the other talking wire, and means associated with the trunk lines for taking reduced potential to said talking wires when the trunk line is busy; service meters associated with the telephone lines, means for interconnecting said meters with the trunk lines when the telephone line is calling, a slow-acting and a quick-acting relay at the called end of the connection adapted to be energized when the conversation takes place and adapted to produce an impulse at the end of the conver sation when the quick-acting relay releases its armature during the retarded action of the slow-acting relay, and means for transmitting said impulse to the meter for registering the conversation.

In testimony wherof, I afiiz; my signature in the presence of two witnesses.

MAX LANGER, WVitnesses FRIEDRICH SPIEOKER, l VILJAHN Mr'iLLnR. 

